P153	The two faces of cathepsin K deficiency in atherogenesis: profibrotic, but lipogenic.
1S.P.Lutgens, 1N.Kisters, 1E.Lutgens, 2M.P.de Winther, 3R.I.van Haaften, 3Chr.T.Evelo, 1M.J.Daemen, 1S.Heeneman, 1K.B.Cleutjens
1Department of Pathology, CARIM, Univerity of Maastricht, Maastricht, NL; 2Department of Molecular Genetics, CARIM, Univerity of Maastricht, Maastricht, NL; 3Department of Bioinformatics, CARIM, Univerity of Maastricht, Maastricht, NL.

Cathepsin K (CatK) was recently found to be differentially expressed during human atherogenesis. To further assess the function of Cathepsin K in atherosclerosis, CatK-/-/ApoE-/- mice were generated. At 26 weeks of age, disruption of CatK reduced total plaque burden by 42 % due to a decrease in the number of advanced lesions as well as individual advanced plaque area. Furthermore, advanced lesions in CatK-/-/ApoE-/- mice showed a 20 % increase in collagen content and a 80 % decrease in the number of elastin breaks underlying the plaque, while initial and advanced lesions showed a 72 and 76 % increase in individual macrophage size respectively. To elucidate pathways by which CatK disruption leads to the observed phenotypic changes, the transcriptomes of aortic arches of CatK-/-/ApoE-/- and ApoE-/- mice were compared. Of 20,280 genes analyzed (Agilent Mouse Oligo Array), 444 showed a significant (p<0.05) over 1.4 fold differential expression. Ingenuity and GenMAPP pathway analysis revealed upregulation of several genes involved in TGFβ-signaling (including the pro-fibrotic genes TGFβ2 (2.6x), LTBP1 (4.3x) and SPARC (2.2x)) and genes involved in lipid trafficking and intracellular transport (including caveolin-1 (6.0x), cav-2 (4.3x), cav-3 (2.2x), CD36 (1.9x) and APP (2.9x)) in CatK-/-/ApoE-/- mice. Differential gene expression was confirmed by Q-PCR and for caveolin-1 and SPARC also at the protein level. The size of oxLDL loaded bone marrow derived macrophages was increased by 300% in absence of CatK, while intracellular cholesterol ester storage increased 32%. Free cholesterol content was not affected. Furthermore, FACS analysis revealed a significant (p=0.03) increase in scavenger receptor mediated uptake of DiI labeled oxLDL by CatK-/-/ApoE-/- macrophages, while electron microscopy showed a 90 % increase in lysosomal size in CatK deficient oxLDL loaded macrophages. In conclusion, our data suggest that CatK deficiency induces plaque stabilization not solely by decreasing proteolytic activity, but also by influencing TGFβ-signaling. Besides this profibrotic effect, CatK deficiency also has a lipogenic effect due to increased lipid uptake possibly mediated by CD36 and caveolins.

Copyright © 2005 S. Karger AG, Basel. Any further use of this abstract requires written permission from the publisher.